We have evaluated the ganglionic blocking action of dopamine and cyclic dopamine analogs. Dopamine inhibits ganglionic transmission in the same dosage range needed for vasopressor activity. Likewise many of the aminotetralin derivatives are potent inhibitors of ganglionic transmission (1.0 microns g/kg). Most of these agents inhibit ganglionic transmission in the same dosage range that is required for inhibition of the adrenergic nerve terminal. There does appear to be differences in sensitivites of various ganglia. Two new aminotetralin analogs have been evaluated that exhibit interesting biological properties. Both agents are potent inhibitors of the adrenergic nerve terminal (ED50-15 micrograms/kg). They have a duration of action greater than 3 hours. They are effective orally. However, in experiments involving the CNS, DK-118 is about 1/3 as active as apomorphine on pre- and post-synaptic sites. DK-121 is inactive at post-synaptic sites and is about 1/3 as active as apomorphine at pre-synaptic sites. If we can develop an agent that is an effective anti-release compound at only presynaptic sites, a new approach for neuroleptic research should result. At least these 2 close structural analogs are certainly different when evaluating activity on the central nervous system. This project summary contained formulas, drawings, tables or nonkeyable data which are not shown above.